Each batch change in an open-end spinning machine results in a reduction of the efficiency of the machine which is caused by a multitude of factors. For example, the lowest downtime and effort is required if a change of the bobbin diameter is made while retaining the type and size of the bobbin tubes. Resetting of the machine to a new raw yarn material, a new fiber or fiber mixture, requires the greatest downtime and effort if, in addition to resetting, the machine must be completely cleaned.
Also, the process of how a batch is finished has a bearing on the efficiency of a spinning machine. As a rule, the end of a batch depends on two possible predetermined events, either at a predetermined time at which, for example, personnel is available for refitting a machine for a fresh batch, or on the amount of the yarn to be produced or the predetermined number of bobbins to be produced. If, for example, based on a predetermined time, the spinning machine is turned off at a set time during the running of a batch, bobbins in different winding conditions will be encountered at the individual spinning stations. Besides full, completely wound bobbins with yarn of first quality, there are also bobbins whose winding condition only permits their classification as bobbins of second quality and so-called remnant bobbins whose amount of yarn is not sufficient for employing them in weaving or knitting mills. While the bobbins of second quality can still be sold at a reduced price, as a rule remnant bobbins cannot be used and are therefore waste. A reduction in the amount of waste is possible only if the remaining yarn can be rewound. However, re-winding depends on whether there still is a usable amount of yarn remaining on a tube. The cost-intensive rewinding process reduces the net revenues which are obtained for bobbins fully wound in this manner.
A batch changing method for winding machines is described in German Patent Publication DE 37 33 788 C2, which is intended to make the production of 100% full cheeses possible. To this end, a number of full bobbins to be attained is preset at the start of the batch, from which the number of winding stations which take part in the production of this batch is subtracted in order to be able to fix the initiation of the ending period of the batch run to the difference formed from these two values. Thereafter, each winding station which has produced a full bobbin is shut down. As a result, the productivity of the winding machine is drastically reduced in the last phase of the batch run. However, the time required for the end phase of the batch run is greatly reduced in comparison with rotor spinning machines because the winding speed of winding machines is approximately ten times that of a rotor spinning machine. Furthermore, a winding machine customarily has maximally 60 winding stations, while as a rule rotor spinning machines typically have more than 200 spinning stations. The amount of the reduction in efficiency in spinning machines is therefore accordingly great.
A flowing batch change during the end phase of the batch run for reducing production losses in connection with open-end spinning machines is not possible in any event because of the group drives employed in such machines.